This invention relates to N,N'-disubstituted p-phenylenediamines which offer protection to polymers such as natural rubber against the deleterious effects of oxygen and ozone. It also relates to methods for preparation and use of these materials and to the compositions formed by mixing these materials with polymers.
Para-phenylenediamines have been used in the past as antioxidants or antiozonants. Some of the patents disclosing such compounds are mentioned below.
N-alkyl-N'-phenyl-p-phenylenediamines are revealed in U.S. Pat. Nos. 3,409,586; 3,424,713; 3,542,691; 3,663,505; and 3,839,275; British Pat. No. 1,035,262; Canadian Pat. Nos. 650,411; 643,839; 609,732; and 882,785; and Australian Pat. No. 285,141.
N,N'-diaryl-p-phenylenediamines are the subject of the following U.S. Pat. Nos.: 3,432,460; 3,510,518 and 3,785,995; British Pat. Nos. 1,047,278; and 1,136,830; and Canadian Pat. No. 789,078.
Sulfur-containing para-phenylenediamines are disclosed in U.S. Pat. No. 3,035,014.
The one-step acid catalyzed reaction between thiols, formaldehyde and aromatic amines is known in the prior art, see P.T.S. Lau and G. F. Grillot, J. Org. Chem., 28, 2763 (1963); J. Org. Chem., 30, 28 (1965); and G. F. Grillot and R. E. Schaffrath, J. Org. Chem., 24, 1035 (1959).